Fresenius' Journal of Analytical Chemistry (09370633)(6)
A sensitive kinetic spectrophotometric method has been developed for the determination of Se(IV) over the range of 45 to 4000 ng in 10 mL of solution. The method is based on the catalytic effect of Se(IV) on the reduction reaction of bromate by hydrazinium dichloride, with subsequent reaction of Ponceau S with products of the above reaction (chlorine and bromine), causing color changing of Ponceau S. Method development includes optimization of time interval for measurement of slope, pH, reagents concentration, and temperature. The optimized conditions yielded a theoretical detection limit of 33 ng/ 10 mL of solution of Se(IV). The interfering effects were studied and removed. The method was applied to the determination of selenium in spiked water, Kjeldahl tablet, selenium tablet, and shampoo. Vanadium(V) has an inhibition effect on the catalyzed reaction of bromate and hydrazine by selenium. Using this effect, V(V) can be determined in the range of 70 to 2500 ng in 10 mL of solution. The optimization procedure includes pH and selenium concentration. An extraction method was used for interference removal. The method was applied to the determination of vanadium in petroleum. © Springer-Verlag 1999.
Journal of Membrane Science (03767388)(2)
The facilitated transport of Au(III) from cyanide solutions through a bulk liquid membrane is reported. The organic phase consisted of a chloroform solution containing Victoria blue dye as the Au(CN)-4 carrier. The effects of pH of source phase, potassium cyanide concentration in source phase, Victoria blue concentration in the organic phase and sodium hydroxide in the receiving phase on the efficiency of transport process were examined. Under optimum conditions the extent of Au(CN)-4 transport across the liquid membrane was about 97% after 180min. The carrier can selectively and efficiently transport Au(CN)-4 ion from the aqueous solutions containing other cations such as alkali and alkaline earth, Zn2+, Pb2+, Cu2+, Cd2+, Hg2+, Ag+, Co2+, Fe2+, Pt2+, Pd2+ and Ni2+. Copyright (C) 1999 Elsevier Science B.V.
Analytica Chimica Acta (00032670)(2-3)
A highly selective and sensitive procedure is presented for the determination of ultra-trace concentrations of molybdenum by catalytic adsorptive stripping voltammetry. The method is based on adsorptive accumulation of the molybdenum (Mo)-methyl thymol blue (MTB) complex onto a hanging mercury drop electrode, followed by reduction of the adsorbed species by voltammetric scan using differential pulse modulation. The reduction current is enhanced catalytically by chlorate. Optimal analytical conditions were found to be a MTB concentration of 0.8μM, pH 2.5, a chlorate concentration of 0.5M, and an adsorption potential at 100mV versus Ag/AgCl. The peak current is proportional to the concentration of molybdenum over the range 0.01-150ngml-1 with a 3σ detection limit of 2pgml-1 with an accumulation time of 60s. The effects of possible interfering ions were studied, and it was found that the proposed procedure is free from interferences of common interfering elements such as tungsten, and iron. The procedure is applied to the determination of molybdenum in a mineral water sample and some analytical grade salts with satisfactory results. Copyright (C) 1999 Elsevier Science B.V.
Transport of Ag+ as Ag(CN)2 - ions through a bulk liquid membrane is reported. The bulk liquid membrane used is a solution of Victoria blue (VB) in chloroform. The effects of pH of the source phase, cyanide concentration in the source phase, sodium hydroxide in the receiving phase, and VB concentration in the organic phase on the efficiency of the transport system were studied. The above system has a high selectivity for Ag+ and can selectively and efficiently transport Ag(CN)2 - ion from aqueous solutions containing other cations such as alkali and alkaline earths, Zn2+, Pd2+, Cu2+, Cd2+, Hg2+, Co2+, Fe2+, Pb2+, Ni2+, and Al3+.
Analytical Letters (00032719)(3)
A technique is presented for the determination of trace amounts of copper(II) by adsorptive cathodic stripping voltammetry. The procedure is based on adsorptive accumulation of copper(II)-Alizarin Red S (ARS) complex on a hanging mercury drop electrode, followed by a stripping voltammetric measurement of the reduction current of the adsorbed complex at -0.16 V (vs. Ag/AgCl). The height of the copper -ARS reduction peak is linearly dependent upon the copper(II) concentration between 0.2-15 and 15-500 ng.ml-1. The detection limit of the technique is 0.05 ng.ml-1 copper(II) for a collection time of 1 minute. The method is free from most interferences. The procedure has been successfully applied to the determination of trace mounts of copper(II) in some analytical grade salts.
Analytica Chimica Acta (00032670)(1-2)
A highly selective and sensitive method is presented for the determination of V(IV), based on its catalytic effect on the oxidation reaction of aniline blue by bromate. The reaction was monitored spectrophotometrically by measuring the decrease in absorbance of aniline blue at 591nm, between 0.5 to 5min (the fixed time method). The effect of various parameters such as pH, concentrations of bromate and aniline blue, temperature and ionic strength on the rate of reaction were studied. The method is free from most interferences, especially from large amounts of V(V). The decrease of absorbance is proportional to the concentration of V(IV) over the entire concentration range tested (5-1200ngml-1) with a 3σ detection limit of 2.0ngml-1 and a relative standard deviation at 60-200ngml-1 V(IV) of ca. 3% (n=3).The method was applied to the determination of V(IV) in river water and some synthetic samples with satisfactory results. Copyright (C) 2000 Elsevier Science B.V.
A very sensitive and selective catalytic adsorptive cathodic stripping procedure for trace measurements of cobalt is presented. The method is based on adsorptive accumulation of the cobalt-MTB (methyl thymol blue) complex onto a hanging mercury drop electrode, followed by reduction of the adsorbed species by voltammetric scan using differential pulse modulation. The reduction current is enhanced catalytically by nitrite. The optimum conditions for the analysis of cobalt include pH 9.0 (ammonia buffer), 2.0 μM methyl thymol blue, 0.8 M sodium nitrite and an accumulation potential of -0.5 V (versus Ag/AgCl). The peak current is proportional to the concentration of cobalt over the entire concentration range tested (0.02-500 ng ml-1) with a detection limit of 0.005 ng ml-1 for an accumulation time of 60 s. The method was applied to determination of cobalt in a mineral water sample and some analytical grade salts with satisfactory results. (C) 2000 Elsevier Science B.V.
